I upgraded to .17.10 and discovered I have no heat pipes (NONE, no copper, silver or gold) in my build menu (checked both hand and assembler). the ones in my base are still in existence, but I cannot build more. FNEI shows them still in my game. Turned off Zombiee's shiny menu's in case there was an issue, but it wasn't.
**update if I'd read your changelogs I would have realized you made a technology update and they're behind a technology gate. I'll leave this up for anyone else who failed to pass the test.

I changed the tech tree structure a little. heatpipes are now on their own technology, if you research that (and heat exchangers 1) you should have access to your lost items again.

This was basically done because in the old structure, 3 different technologies would unlock the heatpipes.

Sorry for the confusion.

Thanks for the quick response, love your work.